1. Field of the Invention
The present invention relates to a power supply device that is installed on a hybrid car, electric vehicle or fuel-cell vehicle and supplies electric power to a driving electric motor for running the vehicle, and a method for detecting the non-contact state of a load connected to a power supply device.
2. Description of the Related Art
A power supply device has been developed that includes a contactor on the output side through which a load is connected to the power supply device (see Japanese Patent Laid-Open Publication No. 2006-216516).
The load connected to this power supply device is a DC/AC inverter. A large-capacitance capacitor is connected in parallel to the input side of the DC/AC inverter. A driving electric motor and an electric generator are connected to the output side of the DC/AC inverter. In the case where this power supply device is connected to the load, when an ignition switch as main switch of a vehicle is turned ON, the contactor is turned ON (closed) so that electric power is provided to the load. When the ignition switch is turned OFF, the contactor is turned OFF so that output voltage is cut off.
In order to determine whether the load is properly connected or is in a non-contact state, the known power supply device includes a connection detecting plug that is constructed integrally with a connector that connects the load to the power supply device so that the connection state of the connector can be detected. The integrally-constructed connection detecting plug is simultaneously connected to the power supply device when the connector is connected to the power supply device. Accordingly, the power supply device can detect that the connection detecting plug is connected, and as a result can detect that the load is detected. The connection detecting plug includes a short circuit that short-circuits a pair of contacts, for example. This type of connection detecting plug short-circuits the contacts that connect the connection detecting plug in the case where the connector is connected, and opens the contacts in the case where the connector is not connected. Accordingly, the power supply device can detect whether a short circuit is established by the connection detecting plug, and as a result can determine whether the connector of the load is connected.
In the thus-constructed power supply device, since the connector necessarily includes the connection detecting plug for detecting the connection state of the load, there is a problem that the construction of the connector becomes complicated. On the other hand, in the case of construction that the load is fastened without using the connector by fastening screws or the like, there is a problem that it is impossible to distinguish whether the connection state or the non-contact state of the load.
The present invention is devised to solve the above problems. It is a primal object to provide a power supply device that is simply constructed without providing a connector with a connection detecting plug for connecting a load or without using a connector but capable of distinguishing whether the connection state or the non-contact state of the load with the load being directly connected to the power supply device.